This invention relates to ultra-high speed electronic circuits for use in microwave and lightwave communication systems, and more particularly, to a frequency demodulator for use in an ultra-high speed digital frequency-shift-keyed (FSK) system.
As the demand for higher capacity communication networks increases, a shift from radio frequency (RF) carrier systems towards microwave and lightwave carrier systems will occur. In such ultra-high speed microwave or lightwave systems, circuitry is required to recover the modulating information signal from the carrier signal for further processing or distribution in the electrical domain. In accordance with traditional prior art RF demodulation techniques, a received modulated carrier signal is mixed with a local oscillator signal to downconvert the RF modulated signal to a baseband signal. Mixers do not presently exist, however, that are capable of such ultra-high speed processing. Accordingly, alternative circuit arrangements are necessary to demodulate such very-high-speed signals.